No, this is not about a plot hook for a comic horror game, although it could be. In fact, why not write one? No, it's about actual castles being for sale, today, right now.
Hunting for some real castle maps, I stumbled on this one. Then I found this site specialising in rather expensive real estate for aspiring nobles. A Dutch site it seems... my fellow countrymen seem to enjoy strange hobbies. This one sells for 25 million gp - eh, euros.
A regular castle may be a bit hard on the average role player's budget, but that's probably precisely why there's quite a few luxurious estates for sale out there. Fancy one? If you do the cleaning, you're welcome to stay in the one I'd buy if I had the money. Which I don't. Ah well.
Gaze and be astounded. And call me if you buy one and want me over. I won't clean ;-)
And enjoy this new year, whatever it may bring!